1. Field of the Invention
The present invention relates to a method for producing 2-sulfonylpyridine derivatives. The 2-sulfonylpyridine derivatives produced by the present invention are useful as starting materials for synthesis of drugs, agricultural chemicals, etc., such as the synthesis starting materials of drug intermediates, including 5-aminomethyl-2-chloropyridine which is useful as an intermediate for synthesis of chloronicotinyl pesticides, 2,5-dichloropyridine which is an intermediate for synthesis of lazabemide, whose clinical development as an anti-Parkinson's disease drug is being promoted, 2-hydroxypyridine, etc. (refer to U.S. Pat. No. 4,897,488, International Patent Application Laid-open No. WO96/26188, International Patent Application Laid-open No. WO98/11071, and Japanese Patent Application Laid-open No. 9-59254).
Moreover, the present invention relates to a method for producing 2-{[(2-pyridyl)methyl]thio}-1H-benzimidazole derivatives. The 2-{[(2-pyridyl)methyl]thio}-1H-benzimidazole derivatives obtained by the present invention are useful as, for instance, intermediates of 2-{[(2-pyridyl)methyl]sulfinyl}-1H-benzimidazole derivatives, compounds related to omeprazole, which is useful as an anti-ulcer agent.
2. Related Art of the Invention
Many physiologically active substances with a pyridine skeleton have been discovered in recent years. As methods for producing 2-sulfonylpyridine derivatives that are useful as intermediates for synthesis of these compounds, there are known, for example:
(1) The method in which sulfonyl cyanide is reacted with an acyloxybutadiene derivative (refer to International Patent Application Laid-open No. WO96/26188); PA1 (2) The method in which p-toluenesulfonyl cyanide is reacted with 1-ethoxy-2-methylbutadiene (refer to Synthesis, p. 623 (1989) and International Patent Application Laid-Open No. WO98/11071); PA1 (3) The synthesis method in which 2-halogenopyridine is reacted with an alkali metal thiolate to produce sulfenylpyridine, and then the sulfenylpyridine is gradually oxidized (refer to Journal of the Chemical Society Perkin Transaction 1, page 1839 (1984)).
However, the above-mentioned methods (1) and (2) have problems in that they have to use a diene compound that is thermally unstable, and the above-mentioned method (3) has problems in that there are many steps, the desired product yield is low, etc., and therefore, these methods can not be considered to be industrially efficient methods for producing 2-sulfonylpyridine derivatives.
In addition, the method in which a 2-halomethylpyridine derivative is reacted with a metal salt of a 2-mercapto-1H-benzimidazole derivative is known as a method for producing a 2-{[(2-pyridyl)methyl]thio}-1H-benzimidazole derivative, and when this is oxidized, a 2-{[(2-pyridyl)methyl]sulfinyl}-1H-benzimidazole derivative can be obtained (refer to U.S. Pat. No. 4,255,431). The 2-halomethylpyridine derivative that is used as the starting material for this method is produced via many steps using 2,3,5-trimethylpyridine as the starting material (refer to, for instance, U.S. Pat. No. 4,544,750 and Japanese Patent Application Laid-open No. 5-70434).
However, conventional methods for producing 2-{[(2-pyridyl)methyl]thio}-1H-benzimidazole derivatives can not be considered to be efficient production methods because many steps are needed to produce the starting 2-halomethylpyridine derivative. Moreover, there are problems in that 2-halomethylpyridine derivatives have poor shelf life and they must therefore be used in the next reaction immediately after synthesis.